1. Field of Invention
The invention relates to a three-port polarization combiner used in a DWDM optic fiber transmission system. In particular, it relates to a passive high-power three-port polarization combiner that can block reverse noises.
2. Related Art
In such an information-dominated era, information communications often become the key factor to great success. The rapid development of the Internet has further made the world as a global village and brought closer the distance among people. It also facilitates the information transmission speed. As the transmission distance and data flow become larger, the need for a higher optical pumping power is more severe.
Because of the above-mentioned requirement, the erbium-doped fiber amplifier (EDFA) and the Raman amplifier appear to be very important. Since the power of existing lasers is insufficient, a set of EDFA and Raman amplifier has to be installed every 40 km along the transmission route. This inevitably increases the cost of the fiber transmission equipment and complicates the maintenance.
To solve this problem, a three-port passive is disclosed to combine two optical pump beams to increase optical pumping power in a DWDM optic fiber transmission system. It provides a high laser power combiner as the pumping source of the EDFA and the Raman amplifier. A photo blocking device is further provided to block reverse noises in the optic fiber communication system, enhancing the system quality.
To provide such a device, many method have been proposed. For example, the U.S. Pat. No. 6,331,913 disclosed a device with combining and separating polarization beams. However, it has the problems of a complicated structure, a higher cost, and a large volume. Moreover, it does not have the function of blocking reverse noises. Therefore, a separate photo blocking device is required.
In view of the foregoing, the invention discloses a three-port optical polarization combiner connected to three optical ports to provide high power. It has a smaller volume and lower cost.
Using the disclosed three-port optical polarization combiner, two optical beams with orthogonal polarizations entering two ports are combined and output via another port.
Another objective of the invention is to provide a three-port optical polarization combiner with the function of blocking reverse noises.
According to the invention, a half-wave plate and a Faraday rotator are inserted into the optical path. By non-reciprocal effect of a half-wave plate and a Faraday rotator, the reverse noise will be blocked to improve transmission quality and protect the laser lens.